Improvement of magnetic recording density of magnetic recording media, such as tapes, cards, discs has been requested more and more leading to severe sliding conditions between a magnetic recording head and a magnetic face. Specifically, a decrease of distance between a magnetic recording head and a magnetic recording face, or an increase of sliding rate occurs leading to requirement of improved performance of lubricants applied to the surface of magnetic recording medium from the viewpoint of duration and utility.
Previously, for example, U.S. Pat. No. 3,715,378 discloses perfluoroethers as lubricants applied to magnetic recording media.
The perfluoropolyethers are excellent lubricants because of superior properties of heat-resistance, chemical inactivity and low vapor pressure. However, the perfluoropolyethers alone are inferior in adsorptivity to a medium which makes it difficult to employ the perfluoropolyethers by itself as a lubricant for magnetic recording medium.
Attempts of converting terminals of perfluoropolyethers into polar groups by the action of which perfluoropolyether lubricants were adhered to a base medium were carried out so as to improve an adsorptivity of the lubricants to the medium (see, U.S. Pat. No. 4,267,238; U.S. Pat. No. 4,268,556; and Japanese Unexamined Patent Publication No. 61-4727).
Lubricants comprising perfluoroalkylpolyethers having polar groups at terminals are adhered to a medium by the action of the polar groups and maintain lubricating properties by perfluoropolyoxy-alkylene chain elongated therefrom.
However, requests for significant improvement of magnetic recording density lead to higher requests for improvement of lubricating properties of lubricant for use in magnetic recording medium. Under these circumstances, even perfluoropolyethers with polar groups are not practically enough in lubricating properties and durability.
It is an object of the invention to provide a lubricant for magnetic recording medium imparting good lubricating properties to magnetic recording medium and a fluorine-containing compound useful as said lubricant.